Projecting a light through a housing to provide information is commonplace. Examples include but are not limited to computer keyboards that include indication lights for functions such as “Caps Lock” or “Num Lock”; computer monitors that include an “on/off” light, automobiles that include lights to indicate whether heated seats are on or off, or whether an air bag is on or off; televisions with indicator lights, and a whole host of other consumer electronics. A common way to provide for such lighting is to provide a projecting light that is visible when the light is off and brightly lit to indicate when the light is on. A collection of lights, or holes for lights, may be disruptive to the objectives of an industrial designer.
One method of attempting to make the holes for lights less visible is to drill very small, tapered holes and fill them with a transparent material. Holes or vias can be formed using mechanical drills, lasers, electrical discharge machining, or chemical etching. A method for producing optical vias is described in co-pending application Ser. No. 11/742,862 PROCESS FOR OPTICALLY TRANSPARENT VIA FILLING, assigned to the assignee of the instant invention. In this method, the vias are drilled, filled with workable transparent material, the filler transparent material set, and then the surface is cleaned to remove excess set transparent material from the visible surface of the article. By workable we mean that the material is in a plastic state, able to be poured or otherwise inserted into the via and conform to the interior shape of the via, thereby sealing it. This process is illustrated in FIGS. 1a-1d. In FIG. 1a, a substrate 10, having a front or cosmetic side 12 and a back side 14, the substrate 10 having a via 16 filled with a transparent filler 18 being irradiated with ultraviolet (UV) radiation 20 from an ultraviolet light source 22 to set the filler 18. FIG. 1b shows the same substrate 10 and via 16 now filled with set filler 24. Note that the UV radiation has penetrated and set filler that extends beyond front side 12 causing a “finger” 26 of cured filler to extend beyond front side 12. In FIG. 1c, a mechanical device such as a blade is used to remove the finger 26 of set material from front side 12 of the substrate 10. The finger 26 of set material can also sometimes be removed by simply wiping with a cloth if the fingers are small enough. FIG. 1d shows the substrate 10 with via 16 filled with set material 24 following removal of finger 26.
FIG. 2 shows a high resolution optical microscope image of a via 30 filled with cured filler 32 taken from the front or cosmetic side 34 of the substrate following removal of excess cured filler. As can be seen in FIG. 2, this process leaves a fractured surface in the cured transparent material 32 on the visible side of the article which can make the via unsightly, more visible when unlit and impairs the lit appearance, all of which are undesirable. Accordingly, there remains a need for a method and apparatus for filling vias with a transparent material without surface fractures to improve their aesthetics both when lit and unlit.